JPH09247475A - Image processing method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress difference in color by a vertical carrying image and a horizontal carrying image and to form an optimum image by converting a prescribed image and a prescribed dither pattern by prescribed angle rotation. SOLUTION: Information on the direction of a page transmitted from a image forming device 2 is analyzed in an analyzing part 11 and it is discriminated whether or not image data is required to be rotated by 90 deg. so as to be developed in output bit map data. Image data obtained by rotating image data by 90 deg. by a rotating part 13 is stored in a storing part 16. The rotating part 13 rotates the dither pattern which is previously stored in a pattern storing part 16 by 90 and, then, the rotated dither pattern is re-stored in the pattern storing part 16. A color processing part 14 inputs rotated image data from the pattern storing part 16, converts them to a CMYK multi-valued signal and its result is stored in the pattern storing part 16. A binarizing part 15 uses the dither pattern in the pattern storing part 16 so as to binarize the image generated in the color processing part 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and method for outputting color image information, and more particularly to an image processing apparatus and method for performing color conversion and binarization processing on input image data.

[0002]

2. Description of the Related Art Generally, in a conventional image processing apparatus represented by a printer apparatus or the like which forms an image based on input color image data, RGB values of color signals handled by a display monitor or the like are input, In general, the signal is color-processed and converted into a CMYK signal which is an output color signal of a printer or the like.

An example of color processing in a conventional general image processing apparatus will be described with reference to FIG. FIG. 1 is a block diagram showing a detailed configuration of color processing in the image processing apparatus. In FIG. 1, multivalued data in RGB notation, which is an input value, is input to a color processing unit 70, subjected to color conversion processing, and converted into a CMYK multivalued signal. In the color conversion process, an n * m matrix operation (masking process) is usually performed on an input RGB signal to obtain a CMYK signal as an output signal.

The masking parameters used here are
It is determined in advance by an arithmetic operation such as the least square method. That is, the parameters are created for the purpose of obtaining the most desirable output signal CMYK for the input signals RGB. The generation of the parameter is not mentioned here. The CMYK multilevel signal output from the color processing unit 70 is
Next, the data is input to the binarization unit 71 and converted into a CMYK binary signal, which is a form when the output unit such as a printer outputs, by dither conversion or the like.

In this dither conversion, a threshold matrix (dither pattern) as shown in FIG. 2 is used to compare one pixel forming an image with the threshold to output the pixel. The data is converted into binary data which is used or not. As described above, color processing in a general image processing apparatus is a signal for the output unit to output an input multivalued signal in RGB notation C
It is to be converted into a MYK binary signal. The printer is a device that performs color reproduction by subtractively mixing CMYK inks in accordance with the obtained CMYK binary signal.

FIG. 3 is a diagram for explaining subtractive color mixing. 181 is a recording medium surface (paper surface), and 182 to 185 are K (black), C (cyan), M (magenta), and Y, respectively.
The (yellow) ink layer is shown. Also, 186 is the space 1
The incident light on 81 and 187 is the reflected light from the paper surface 181. As shown in FIG. 3, the printer forms a color image by superposing CMYK ink layers 182 to 185 on the paper surface 181. In this case, the incident light 186 reflects the ink layer 18
2 to 185, reaches the paper surface 181, is reflected there, and again passes through the ink layers 182 to 185 and is reflected light 1
The observer is reached as 87. In the process, energy is sequentially absorbed by the ink layers 182 to 185 having different spectral absorptances, the spectral characteristics of light are changed, and colors are reproduced.

Next, the flow of image processing in the conventional image processing apparatus will be described. FIG. 4 is a block diagram showing the flow of image processing. In FIG. 4, the image data sent from the application or the like is first analyzed by the analysis unit 31, and then expanded by the expansion unit 32 into a form suitable for outputting bitmap data or the like at 32 according to the analysis result. To be done. The bitmap data is output by the output unit 33.
Is output by an output device such as a printer.

Next, the rotation of the page in the image processing apparatus will be described with reference to FIG. Where 21, 22
Are image data created by applications or the like, and are usually created according to the size of the output paper. The vertically long image data such as 21 is called a portrait image, and the horizontally long image data like 22 is called a landscape image.

Reference numerals 23 and 24 respectively indicate the conveyance direction of the output paper when an image is output by an output device such as a printer.
A horizontally long transport such as 4 is called a horizontal transport. here,
When outputting portrait image 21 by vertical conveyance 23,
When the landscape image 22 is output by the lateral conveyance 24, the image data may be directly expanded into output bitmap data.

However, when the portrait image 21 is output by the horizontal transport 24 or when the portrait image 22 is output by the vertical transport 23, the image data is rotated by 90 degrees and expanded into bitmap data for output. There is a need to. Here, the flow of the above-described expansion processing in the image processing will be described in more detail using the flowchart shown in FIG.

In FIG. 6, first, in step S41, it is necessary to rotate the image as in the case where the portrait image 21 is output by the horizontal conveyance 24 or the landscape image 22 is output by the vertical conveyance 23. Determine if there is. Then, if it is not necessary to rotate it, the process proceeds to step S43. If it is necessary to rotate, rotation processing is performed in step S42.

Next, in step S43, the above-described color processing is performed. Next, in step S44, binarization processing is performed, and the obtained binary image data is expanded as bitmap data for output. In the case of color image output, the bitmap data is usually an output signal CM.
Separately prepared for YK. An outline of bitmap data will be described with reference to FIG.

In FIG. 7, 51 is a vertical conveyance image,
52 is the origin, and the upper left point is normally used. Also,
Reference numeral 53 is a lateral conveyance image, 54 is its origin, and the lower left point is normally used. Reference numeral 55 is a bit map memory for expanding the bit map data, and stores the bit map data according to the carrying direction indicated by the arrow in the figure. That is, in the case of the vertical conveyance image 51, one raster is expanded in the horizontal direction from the origin 52 and sequentially expanded in the downward direction.

Further, in the case of the laterally conveyed image 53, one raster is expanded in the horizontal direction from the origin 54 and sequentially expanded in the upward direction. At this time, the dither pattern shown in FIG. 2 used for the above-mentioned binarization is conceptually spread repeatedly starting from the upper left of the bitmap memory. That is, the horizontal size of the bitmap memory is X
Assuming that the pixel is Y pixels in the vertical size, in the case of the 8 * 8 pixel dither pattern as shown in FIG.
/ 8 to X / 8 + 1 times, and Y / 8 to Y / 8 + 1 times in the vertical direction.

That is, as shown in FIG. 7, in the case of binarization, a dither pattern spread in a bit map memory is used. The binarization process is performed, and binarization is sequentially performed in the downward direction. Further, in the case of the vertically conveyed image 53, binarization processing for one raster is performed in the horizontal direction from the origin 54, and binarization is sequentially performed in the upward direction.

These bit map memories are 55 to 5
As shown in FIG. 8, it is prepared for each of CMYK, and at the time of output, an image is formed by sequentially sending CMYK bitmap data to the output device.

[0017]

In the conventional example described above, since the vertical carrying image and the horizontal carrying image are developed at different addresses in the bit map memory, the dither pattern for binarization is used. Phase difference occurs. That is, it can be said that the dither pattern is slightly different between the vertically conveyed image and the horizontally conveyed image.

This causes the problem shown in FIG. In FIG. 8, reference numerals 61 and 62 are schematic views showing a state in which a highlight image is processed by a dither pattern of vertical conveyance and horizontal conveyance, respectively. In FIG. 8, circle marks, triangle marks, square marks, and star marks respectively correspond to outputs of C, M, Y, and K inks. The highlight image is a bright image with a constant density, and is an image in which the number of output pixels per unit area is relatively small. 61, 6 for uniform highlight images
As shown in FIG. 2, the difference in the image after binarization due to the difference in the dither pattern appears remarkably. That is, the tint is different depending on the type of ink having a large proportion in the unit area.

On the other hand, in the case of the high density images shown by 63 and 64, unlike the highlight image, the number of output pixels per unit area is large, so the image after binarization is stable at a high density, Output difference due to transport and lateral transport is unlikely to appear.
That is, in the above-mentioned conventional example, when the same original image is processed due to the difference in the dither pattern between the vertical conveyance and the horizontal conveyance, there is a drawback that the tint particularly in the highlight image is different.

The present invention has been made in view of the above conventional example, and an object of the present invention is to provide an image processing method and an apparatus therefor capable of optimal image formation for suppressing the difference in color tint between a vertically conveyed image and a horizontally conveyed image. And

[0021]

In order to achieve the above object, an image processing method and apparatus according to the present invention have the following arrangement. That is, an image rotation conversion step of rotating and converting a predetermined image by a predetermined angle, a dither pattern rotation conversion step of rotating and converting a predetermined dither pattern by the predetermined angle, and a rotation image rotated in the image rotation step as an image. From the image of the image formable color space converted in the image conversion process, using the image conversion process of converting into the image of the formable color space and the dither pattern rotated and converted in the dither pattern rotation conversion process. A binary image generating step of generating a value image.

Another aspect of the present invention is an image rotation conversion step for rotating and converting a predetermined image at a predetermined angle, and an image for converting the rotation image rotated in the image rotation step into an image in a color space capable of forming an image. If the conversion step and the predetermined image are portrait images, a dither pattern for portrait is used to generate a binary image of the image formable color space image converted in the image conversion step, and If the predetermined image is a landscape image, a generating step of generating a binary image from the image of the image formable color space converted in the image converting step using a landscape dither pattern is included. The dither pattern for landscape and the dither pattern for landscape are in a 90-degree rotation relation with each other.

Another aspect of the present invention is an image rotation conversion step of rotating and converting a predetermined image by a predetermined angle, and an image of converting the rotation image rotated in the image rotation step into an image in a color space capable of forming an image. A converting step and a generating step of generating a binary image from the image of the image-formable color space converted in the image converting step using a highlight dither pattern if the predetermined image is a highlight image With.

Further, according to another invention, an image rotation converting means for rotating and converting a predetermined image at a predetermined angle, a dither pattern rotation converting means for rotating and converting a predetermined dither pattern at the predetermined angle, and the image rotating means. Image conversion means for converting the rotated rotated image into an image in a color space capable of forming an image, and image formation converted by the image conversion means using the dither pattern rotated and converted by the dither pattern rotation converting means. And a binary image generating means for generating a binary image from an image in a possible color space.

Another aspect of the present invention is an image rotation conversion means for rotating and converting a predetermined image at a predetermined angle, and an image for converting the rotation image rotated by the image rotation means into an image in a color space capable of forming an image. If the conversion unit and the predetermined image are portrait images, a dither pattern for portrait is used to generate a binary image from the image of the image-formable color space converted by the image conversion unit, If the predetermined image is a landscape image, the landscape dither pattern is used to generate a binary image of the image in the image-formable color space converted by the image conversion unit, and the portrait image is generated. The dither pattern for landscape and the dither pattern for landscape are in a 90-degree rotation relation with each other.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, after summarizing the points of an image processing method and an image processing apparatus according to an embodiment of the present invention, a detailed description thereof will be given. An image processing method and apparatus according to an embodiment of the present invention include a rotation processing unit for rotating image data by 90 degrees, a color processing unit for performing color processing, and a binarization for performing binarization. Section and a pattern storage section for storing a dither pattern used in the binarization section.

Here, the rotation processing unit rotates the bitmap data for image output and the dither pattern. Also,
The pattern storage unit stores a pattern for a portrait image and a pattern for a landscape image. Further, it is provided with a dither pattern selection unit for selecting a dither pattern for a portrait image and a dither pattern for a landscape image in accordance with an instruction from the outside whether or not the input image data is a highlight image.

Further, it has an analysis unit for analyzing the input image data and a highlight detection unit for determining whether or not the input image data is a highlight image. Further, the dither pattern selection unit selects a dither pattern for portrait image and landscape image according to the determination by the upper illite detection unit. Further, it has an image output unit that forms an image based on the output data created through the color processing unit and the binarization unit.

In the above arrangement, there is provided a method of using a common dither pattern for a vertically conveyed image and a horizontally conveyed image for a highlight image and binarizing a conventional example for a high density image. As a result, optimum color reproduction is possible, and a unique effect that ideal color reproduction can be obtained is obtained. In each of the embodiments described below, an inkjet type color printer is used as an example, but it goes without saying that other output devices such as a color printer of another type can be similarly implemented.

The image processing method and apparatus according to the embodiment of the present invention will be described below in detail. [First Embodiment] In the present embodiment, analysis means for analyzing image data sent from an application and image data such as page orientation such as portrait and landscape, and the image according to the analysis result by the analysis means. Expansion means for expanding the data into bitmap data for output, color processing means for forming a part of the expansion means for performing color processing on the input data at the time of expansion by the expansion means, and The binarizing means forming a part of the expanding means for binarizing the applied data, and the binarizing means are binary.
A pattern storage unit for storing a dither pattern used for binarization, and the image data and the dither pattern
Rotating means forming a part of the expanding means for rotating by 0 degrees, bitmap storing means for storing the bitmap data expanded by the expanding means, and data in the bitmap storing means to an output device. By providing output means for holding data such as output and paper conveyance direction of the output device, the result of analysis of the page orientation information sent from the application by the analysis means and the output means are held. The necessity of rotation of the image data is determined based on the direction of paper conveyance of the output device, and if necessary, the image data is rotated by 90 degrees by the rotation means which is a constituent element of the expanding means, and the pattern is further rotated. After rotating the dither pattern in the storage means by 90 degrees, the image data sent from the application is analyzed according to the analysis result by the analysis means. Te, after performing the processing by the color processing means in said expanding means, said performs binarization using the dither pattern in the pattern storing unit by the binarizing means, and then stored in the bitmap storage unit. Therefore, in the present embodiment,
Since it is possible to create bitmap data using an in-phase dither pattern in an ndscape image,
It is possible to perform color reproduction that suppresses the difference in color tint due to the portrait and landscape images.

The present embodiment will be described in detail below. FIG. 9 is a block diagram showing the configuration of the image processing apparatus according to the embodiment of the present invention. In FIG. 9, 1 is an image processing apparatus according to the present embodiment. Reference numeral 2 is an original image creating apparatus that creates an application image, and 3 is an image output apparatus that forms an output image based on output data from the image processing apparatus 1.

In the image processing apparatus 1, reference numeral 11 is an analysis unit 11 for analyzing image data transmitted from an application and input data regarding page orientation such as portrait and landscape images. 12 is the analysis unit 1
1 is a decompression unit that performs various drawing processes according to the content analyzed by 1 and stores the generated bitmap data in the bitmap storage unit 17. Bitmap storage unit 1
The bitmap data stored in 7 is stored in the image output unit 18
Is read out and output to the image output device 3 to form an image.

Reference numeral 13 denotes a rotation unit 13 in the expansion unit 12 for rotating the bit map data and the dither pattern stored in the pattern storage unit 90 by 90 degrees.
A color processing unit 14 is provided in the expansion unit 12 and performs the above-described color processing. 15 is in the expansion unit 12,
It is a binarization unit that performs binarization processing using the dither pattern stored in the pattern storage unit 16.

Reference numeral 16 is a pattern storage unit for storing the dither pattern used when the binarization unit 15 performs the binarization process. The pattern storage unit 16 also stores the processing results of the rotation unit 13, the color processing unit 14, and the binarization unit 15. 17
Is a bitmap storage unit 17 for storing the bitmap data, which is the data to be output to the above-described output device, which is expanded by the expansion unit 12.

Reference numeral 18 denotes an image output unit that outputs the bitmap data in the bitmap storage unit 17 to the image output device 3 and holds data such as the paper conveyance direction of the image output device 3. In the present embodiment, the image output device 3 is, for example, an m inkjet printer.

In the image output section 18, the output data is bitmap data for one page, and is composed of four colors of CMYK as described above. The image output unit 18 sends the output data to the image output device 3. Then, the image output device 3 receives the image and outputs the image to the output sheet by using each ink of C (cyan), M (magenta), Y (yellow), and K (black).

The procedure of image processing in the developing unit 12 in the present embodiment having the above configuration will be described below with reference to the flowchart shown in FIG. FIG. 10 shows the expansion unit 12.
Is a flow chart showing the flow of processing when data for one page is input and data for output is formed. In FIG. 10, first, in step S81, the result of analysis of the page orientation information sent from the image creating apparatus 2 by the analysis unit 11 and the paper conveyance of the image output apparatus 3 held in the image output unit 18 are performed. Depending on the orientation data, the image data may be rotated by 90 degrees for output, as in the case where the portrait image 21 in FIG. 5 is output by the horizontal conveyance 24 or the landscape image 22 is output by the vertical conveyance 23. Determine the need to expand to the bitmap data of.
If it is necessary, the process proceeds to step S82. Otherwise, it proceeds to step S84.

In step S82, the image data obtained by rotating the image data by 90 degrees by the rotation unit 13 of the development unit 12 is stored in the pattern storage unit 16. In step S83, the rotation unit 13 rotates the dither pattern stored in the pattern storage unit 16 by 90 degrees. Then, the rotated dither pattern is stored again in the pattern storage unit 16. This rotated dither pattern is used in the process in the binarization unit 15 described later.

In step S84, the color processing unit 14 inputs the rotated image data from the pattern storage unit 16 if the image data has been subjected to the rotation process, and if the image data has not been subjected to the rotation process, the developing unit 12 does. Input the image data input to. Then, the image data (multivalued data in RGB notation) is converted into a CMYK multivalued signal. Then, the conversion result is stored in the pattern storage unit 16.

In this color conversion processing, normally, an input RGB signal is subjected to n * m matrix calculation (masking processing) or the like to obtain a CMYK signal as an output signal. Next, in step S85, the binarization unit 15 uses the dither pattern in the pattern storage unit 16 described above,
The image (stored in the pattern storage unit 16) generated by the color processing unit is binarized.

As described above, the binarization process uses the dither pattern as shown in FIG. 2 to compare one pixel forming the image with the threshold value and output the pixel. It is to be converted into binary data. In the above-mentioned conventional example, as shown in FIG.
In the case of the vertical conveyance image 51, the dither pattern spread in the bit map memory is used to set 1 in the horizontal direction from the origin 52.
Binarization processing for the raster is performed, and the binarization processing is sequentially performed downward.

In the case of the horizontally conveyed image 53, binarization processing for one raster is performed horizontally from the origin 54, and binarization processing is sequentially performed in the upward direction. In the present embodiment, since the dither pattern is also rotated in accordance with the rotation of the image data, it is considered that the dither pattern is conceptually attached to the original image itself rather than the bitmap memory.

Therefore, for example, when a portrait image and a landscape image having the same image data are output to a printer in the vertical conveyance direction, as a result, binarization is performed with a dither pattern having the same phase. You can As described above, according to the present embodiment, since it is possible to create bitmap data using in-phase dither patterns, it is possible to achieve color reproduction that suppresses color differences between portrait images and landscape images. It becomes possible, and optimal color reproduction becomes possible.

[Second Embodiment] The second embodiment according to the present invention will be described in detail below. In the first embodiment described above, the dither pattern in the pattern storage unit 16 is rotated when the rotating unit 13 needs to rotate, whereas in the second embodiment, the dither pattern is previously used for portrait. A dither pattern for landscape is prepared in the pattern storage unit 16 and selectively used.

Here, as the landscape dither pattern, a pattern in which the portrait pattern is rotated by 90 degrees and the starting points thereof are matched is used. That is, in step S83 shown in FIG. 10 of the first embodiment, the rotating unit 13
While rotating the dither pattern by
In the second embodiment, the binarization is performed by using a pattern that has been rotated by 90 degrees in advance during binarization.

Therefore, in the image processing apparatus of the second embodiment, the basic configuration is the same as that of the above-mentioned first embodiment, but the processing and control method for the rotation of the rotating unit 13 are the same as those of the first embodiment. The number of types of storage patterns in the pattern storage unit 16 is different. Hereinafter, parts different from the above-described first embodiment will be described. The flow of color processing in the second embodiment is shown in the flowchart of FIG.

FIG. 11 shows the configuration of FIG. 10 in the first embodiment.
9 is a flowchart showing a flow of processing when the expansion unit 12 inputs data for one page and forms data for output, similarly to the above. In FIG. 11, first, in step S 91, the result of analysis of the page orientation information sent from the original image creating apparatus 2 by the analysis unit 11 and the paper conveyance orientation of the image output apparatus 3 held in the image output unit 18 The horizontal transfer 24 of the portrait image 21 shown in FIG.
If you want to output the
As in the case of outputting in 3, the image data is rotated by 90 degrees, and it is determined whether it is necessary to expand the bitmap data for output. If necessary, step S92
Proceed to. If not, the process proceeds to step S93.

In step S92, the rotation unit 13 stores the input image data rotated 90 degrees in the pattern storage unit 16. In step S93, the color processing unit 1
If the image data has undergone rotation processing, 4 inputs the rotated image data from the pattern storage unit 16, and if not, inputs the input image data to the expansion unit 12. Then, the image data (RG
(B-valued multivalued data) is converted into a CMYK multivalued signal.
Then, the conversion result is stored in the pattern storage unit 16.

In step S94, it is determined whether the original image is portrait or landscape. If the original image is a portrait, the process proceeds to step S95.
If it is a landscape, the process proceeds to step S96. In step S95, the binarization unit 15 selects the portrait dither pattern in the pattern storage unit 16.

In step S96, the binarization unit 15 selects the landscape dither pattern in the pattern storage unit 16. Next, in step S97, the binarization unit 15
Performs binarization of the image (stored in the pattern storage unit 16) generated by the color processing unit using the selected dither pattern.

In the first embodiment described above, since the dither pattern is also rotated in accordance with the rotation of the image data, it is considered that the dither pattern is conceptually attached to the original image itself rather than the bitmap memory. In the present embodiment, different patterns are used in advance depending on the orientation of the original image. However, as the landscape dither pattern, a pattern in which the portrait pattern is rotated by 90 degrees and the starting points thereof are matched is used.

Therefore, for example, when the portrait image and the landscape image having the same image data are output to the printer in the vertical conveyance direction, the first image is eventually output.
Similar to the above embodiment, the binarization can be performed with the dither pattern having the same phase. As described above, according to the present embodiment, since it is possible to create bitmap data using dither patterns having the same phase, it is possible to perform color reproduction that suppresses the difference in color tint between portrait and landscape images. Therefore, optimum color reproduction is possible.

[Third Embodiment] The third embodiment of the present invention will be described in detail below. In the above-described first embodiment, the dither pattern of the pattern storage unit 16 is rotated when the rotating unit 13 needs to rotate. In the above-described second embodiment, the dither pattern is rotated in advance for portrait. A dither pattern for landscape is prepared in the pattern storage unit 16 and selectively used. In either case, fixed processing was performed regardless of the characteristics of the original image, but in the present embodiment, means for externally instructing whether or not the original image is a highlight image and the instruction The dither patterns for the highlight image and the high density image are selected according to the above.

Here, in order to clarify the characteristics of the present embodiment, the problem in the conventional highlight image will be described again with reference to FIG. FIG. 8 is a schematic diagram showing a state in which the highlight images 61 and 62 are processed by a dither pattern of vertical conveyance and horizontal conveyance, respectively. A circle mark, a triangle mark, a square mark, and a star mark correspond to outputs of C, M, Y, and K inks, respectively. The highlight image is a bright image with a constant density, and is an image in which the number of output pixels per unit area is relatively small. 61, 62 for uniform highlight images
As shown in (3), the difference between the binarized images due to the different dither patterns is remarkable. That is, in the unit area, the tint varies depending on the type of ink having a large proportion.

On the other hand, in the case of the high density images shown by 63 and 64, the number of output pixels per unit area is large unlike the highlight image, so that the binarized image is stable at a high density, Output difference due to transport and lateral transport is unlikely to appear.
However, a problem arises when a high-density image is binarized by using the binarization method shown in the above embodiment. These problems will be described with reference to FIGS.

FIG. 12 is a diagram showing how the ink jet printer forms an image. In FIG. 12, 15
Reference numeral 1 denotes a head for ejecting CMYK ink onto the output paper 154 to form an image.
It is composed of a plurality of nozzles such as four nozzles. 1
Reference numeral 52 is a CR motor for moving the head vertically to the insertion direction of the output paper 154. Also, 15
Reference numeral 3 is an LF motor for conveying the output paper in the insertion direction. An image is formed on the output paper 154 by moving the head 151 in cooperation with the CR motor 152 and the LF motor 153. With such a configuration, the head 151 moves once (pass) by the CR motor 152.
An image of vertical 64 dots is formed by.

Next, referring to FIG. 13, an output result in the ink jet printer having the configuration shown in FIG. 12 is shown. In FIG. 13, reference numeral 161 denotes an output image of the first pass and the second pass of the output image 161 for one page of each output sheet. That is, the output image 161 is formed through a plurality of passes of 64 dots vertically as described above. In image formation by such a method, image discontinuity (or interference fringes) occurs between passes as shown in FIG. 13, and appears as horizontal stripes on the output image. These discontinuities are CR in FIG.
It is conceivable that it is difficult to keep the distance between each pass in one pass of the head constant due to the deviation of the head and the paper feed by the motor 152 and the LF motor 153.

Horizontal stripes due to such discontinuity are more likely to occur in a high-density image having a higher density than in a highlight image with sparse dots. Various methods have been conventionally devised to prevent such horizontal stripes, but one solution is a method using a certain dither pattern. This is to strengthen the connection of the image data between the paths like 162 and 163 in FIG. 13 by using a dither matrix that grows vertically as shown in FIG. As described above, since the dither pattern in consideration of the characteristics of the image output device is formed in consideration of the paper carrying direction, the dither pattern is rotated by 90 degrees with respect to the paper carrying direction as in the above-described embodiment. In some cases, the effect of such dither patterns may be diminished. In particular, when a dither pattern rotated by 90 degrees with respect to a high density image is used, there is an adverse effect that horizontal stripes are emphasized.

Therefore, in this embodiment, in addition to the conventional binarization method for preventing horizontal stripes in a high-density image, a binarization method suitable for processing a highlight image is provided, and an original image is provided. Means for externally instructing whether or not is a highlight image, and by switching the binarization method described above, horizontal stripes in the high-density image can be suppressed, and the vertical conveyance image in the highlight image, It is intended to obtain the optimum color reproduction that suppresses the difference in color tint due to the conveyed image.

Therefore, in the image processing apparatus of the third embodiment, the basic structure is the same as that of the first embodiment described above, but it is externally selected whether or not the original image is a highlight image. The selection means for selecting the dither pattern for the highlight image and the dither pattern for the high density image according to the instruction, and the control method thereof are different. Hereinafter, parts different from the above-described first embodiment will be described.

FIG. 15 is a block diagram showing the arrangement of an image processing apparatus according to the third embodiment of the present invention. 15 is different from FIG. 9 showing the first embodiment in that a selection unit 19 for externally selecting whether or not the original image is a highlight image is additionally configured.

16A and 16B show an example of external display by the selection unit 19 in the third embodiment. That is, the selection unit 19 causes the operator who uses the image processing apparatus of the present embodiment to select whether or not the original image is a highlight image. For example, the display shown in FIGS. 16A and 16B is displayed on a monitor (not shown), and the selection unit 1
9 recognizes that the highlight image is not selected (high density selection state) in FIG. 16A and the highlight image is selected in FIG. 16B by an operator's input from a mouse or a keyboard (not shown). Next, the flow of color processing in the third embodiment is shown in the flowchart of FIG.

FIG. 17 shows the configuration of FIG. 10 in the first embodiment.
9 is a flowchart showing a flow of processing when the expansion unit 12 inputs data for one page and forms data for output, similarly to the above. In FIG. 17, first, in step S111
Then, the portrait image in FIG. 5 is obtained according to the result of the analysis of the page orientation information sent from the application 2 by the analysis unit 11 and the paper conveyance orientation of the image output device 3 held in the image output unit 18. 21 lateral transport 2
4, it is necessary to rotate the image data by 90 degrees and expand the bitmap data for output, as in the case of outputting the landscape image 22 by the vertical conveyance 23. In step S112, the image data rotated by 90 degrees by the rotation unit 13 is stored in the pattern storage unit 16.

If it is determined in step S111 that it is not necessary to rotate, the process proceeds to step S113. In step S113, the color processing unit 14 inputs the rotated image data from the pattern storage unit 16 if the image data is rotated, and inputs the rotated image data to the developing unit 12 if the image data is not rotated. Input the image data. Then, the image data (multivalued data in RGB notation) is commercialized.
Convert to YK multilevel signal. Then, the conversion result is stored in the pattern storage unit 16.

In step S114, the selection unit 19
Determines whether the original image is a highlight image or a high-density image selected by the operator. If the original image is highlighted, the process proceeds to step S115. On the contrary, if not, the process proceeds to step S116.
In step S115, if the original image is a portrait, the binarization unit 15 selects the highlight. Select a dither pattern for portrait. If the original image is a landscape, highlight. Select a landscape dither pattern.

Here, the highlight. The dither pattern for landscape is the above highlight. This is a pattern in which the portrait dither pattern is rotated 90 degrees in advance and the starting points thereof are made the same, and the effect is the same as that of the second embodiment. In step S116, the binarization unit 15
A high density dither pattern in the pattern storage unit 16 is selected.

Here, the selection of the high density dither pattern is the processing as shown in the above-mentioned conventional example. That is,
As shown in FIG. 7, when binarizing, the vertical conveyance image 51 is formed by using the dither pattern spread in the bitmap memory.
In the case of, binarization processing for the raster is performed in the horizontal direction from the origin 52, and binarization is sequentially performed in the downward direction. Further, in the case of the laterally-conveyed image 53, two rasters are horizontally provided from the origin 54.
By performing the binarization process and binarizing in the upward direction, a pattern that always suppresses the occurrence of horizontal stripes is used.

Next, in step S117, the binarization unit 1
In step 5, binarization is performed by applying the selected dither pattern to the CMYK multivalued image obtained as a result of the processing in step S113. As described above, in the above-described first and second embodiments, the rotated dither pattern is used regardless of whether the image data is a highlight image or not, and therefore horizontal stripes are generated in the case of a high-density image. However, in the present embodiment, since the binarization processing is switched corresponding to the highlight image and the high density image, it is possible to perform the optimum color reproduction suitable for each image.

As is clear from the above description, the third
The embodiment can be carried out independently of the first and second embodiments described above, or simultaneously. [Fourth Embodiment] The fourth embodiment of the present invention will be described in detail below.

In the third embodiment described above, means for externally instructing whether or not the original image is a highlight image, and dither patterns for highlight image and high density image are selected in accordance with the instruction. On the other hand, in the present embodiment, means for automatically detecting whether or not the original image is a highlight image is provided. That is, the effect to be obtained in the present embodiment is similar to that of the third embodiment, and the basic configuration is similar to that of the above-described third embodiment. As shown in FIG. 18, the selection unit 19 in the third embodiment performs
The difference is that the highlight detection unit 20 determines whether or not the original image is a highlight image without the operator's operation, and the control method thereof.

The parts different from the above-described third embodiment will be described below. The highlight detection unit 20 in the fourth embodiment extracts only the image signal data from the analysis unit 11 that analyzes the input data from the original image creating device 2,
By further statistically analyzing the image signal data,
The highlight image is detected. The flow of processing in the highlight detector 20 is shown in the flowchart of FIG.
In FIG. 19, in step S141, cou, which is a counter for counting the total number of pixels of the image signal.
nter and Hcnt, which is a counter for counting the number of highlight pixels, are cleared.

Next, in step S142, it is checked whether or not all the processing relating to the image signal to be detected has been completed. This is performed based on the information from the analysis unit 11 and the like. If it is determined in step S142 that all the pixel signals have not been completed, the pixel signal is evaluated in step S143 as follows. Incidentally, here, the input pixel signal is assumed to be an RGB signal.

In this evaluation, the R signal value is larger than T1 which is a predetermined threshold value, the G signal is larger than T2 which is a predetermined threshold value, and the B signal value is It is evaluated whether or not it is larger than T3 which is a predetermined threshold value. That is, when all the input RGB values are larger than a certain threshold value, it is determined that the pixel is a highlight, and the counter Hcnt is incremented in step S144.

If the evaluation in step S143 is false, the process proceeds to step S145. In step S145,
The counter counter is incremented, and the process again proceeds to step S142. If it is determined in step S142 that the evaluation of the image signal to be detected has been completed, in step S146, c of Hcnt is determined.
It is evaluated whether or not the ratio occupied in the outer is larger than the predetermined threshold value T4. Where if true, then
It is determined that the input image data is a high density image.

Threshold values T1 to T4 used here
, An optimum value is obtained in advance. How to obtain the optimum solution of the threshold value will not be mentioned here. The flow of image processing in this embodiment is the same as that in FIG. 17, which is a flowchart showing the flow of the third embodiment described above, but step S114.
In the above-described third embodiment, the selection unit 19 determines whether the operator has selected the original image as a highlight image or a high-density image, whereas in the present embodiment, The highlight detection unit 2 described above
The determination is made according to the detection result of 0.

As described above, in the above-described third embodiment, means for externally instructing whether or not the original image is the highlight image, and for the highlight image and the high density image according to the instruction. However, in the present embodiment, by providing means for automatically detecting whether or not the original image is a highlight image, no operator intervention is required. In addition, optimum color reproduction suitable for each image becomes possible.

As is clear from the above description, the fourth
The embodiment can be carried out independently or simultaneously with the above-described first and second embodiments. The present invention may be applied to a system including a plurality of devices or an apparatus including a single device.
Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

Further, an object of the present invention is to supply a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (or CPU) of the system or the apparatus.
And MPU) read and execute the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, C
A D-ROM, a CD-R, a magnetic tape, a non-volatile memory card, a ROM, etc. can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) May perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

When the present invention is applied to the above storage medium, the storage medium stores the program code corresponding to the above-described flowchart.
As described above, by using a common dither pattern for the vertically-conveyed image and the horizontally-conveyed image, it is possible to suppress the color difference between the vertically-conveyed image and the horizontally-conveyed image.

Further, it becomes possible to provide a method for performing binarization of a conventional example for a high density image by using a common dither pattern for a vertical transportation image and a horizontal transportation image for a highlight image, More ideal color reproduction can be obtained.

[0084]

As described above, according to the present invention, it is possible to form an optimum image that suppresses a difference in color tint between a vertically conveyed image and a horizontally conveyed image.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an outline of conventional image processing.

FIG. 2 is a diagram showing an example of a dither pattern.

FIG. 3 is a diagram illustrating subtractive color mixture in image output.

FIG. 4 is a block diagram showing an outline of a flow of conventional image processing.

FIG. 5 is a diagram illustrating an example of rotation of image data.

FIG. 6 is a flowchart showing an image processing procedure in a developing unit in FIG.

FIG. 7 is a diagram showing a configuration concept of a bitmap memory.

FIG. 8 is a diagram illustrating a problem in a conventional example.

FIG. 9 is a diagram showing a configuration example of an image processing apparatus according to an embodiment of the present invention.

FIG. 10 is a flowchart showing a procedure of image processing in a developing unit according to the first embodiment of the present invention.

FIG. 11 is a flowchart showing the procedure of image processing of the second embodiment according to the present invention.

FIG. 12 is a diagram illustrating an output of an inkjet printer.

FIG. 13 is a diagram illustrating an output result of the inkjet printer.

FIG. 14 is a diagram showing an example of a dither pattern.

FIG. 15 is a diagram showing a configuration example of an image processing apparatus according to a third embodiment of the present invention.

FIG. 16A is a display example in the selection unit in the third embodiment.

FIG. 16B is a display example in the selection unit in the third embodiment.

FIG. 17 is a flowchart showing the procedure of image processing according to the third embodiment of the present invention.

FIG. 18 is a diagram showing a configuration example of an image processing apparatus according to a fourth embodiment of the present invention.

FIG. 19 is a diagram showing a processing procedure of a highlight detection unit in the fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image processing device 11 Analysis unit 12 Development unit 13 Rotation unit 14 Color processing unit 15 Binarization unit 16 Pattern storage unit 17 Bitmap storage unit 18 Output unit 19 Selection unit 20 Highlight detection unit

Claims (22)

[Claims] 1. An image rotation conversion step of rotating a predetermined image by a predetermined angle, a dither pattern rotation conversion step of rotating a predetermined dither pattern by the predetermined angle, and a rotation rotated in the image rotation conversion step. An image conversion step of converting an image into an image in a color space capable of forming an image, and the dither pattern rotated and converted in the dither pattern rotation conversion step, and using the dither pattern converted in the image conversion step. And a binary image generating step of generating a binary image from the image. 2. The image processing method according to claim 1, wherein the predetermined image is an image in an RGB color space. 3. The image of the color space in which the image can be formed is C
The image processing method according to claim 1, wherein the image is an image in the MY color space. 4. The image processing method according to claim 1, wherein the predetermined angle is 90 degrees. 5. The image processing method according to claim 1, wherein the predetermined image is a portrait image. 6. The image processing method according to claim 1, wherein the predetermined image is a landscape image. 7. The image processing method according to claim 1, further comprising an image forming step of forming an image based on the image generated in the binary image generating step. 8. An image rotation conversion step of rotating a predetermined image by a predetermined angle, and an image conversion step of converting the rotated image rotated in the image rotation conversion step into an image in a color space capable of forming an image. If the predetermined image is a portrait image, a dither pattern for portrait is used to generate a binary image of the image in the image-formable color space converted in the image conversion step, and the predetermined image is generated. In the case of a landscape image, a landscape dither pattern is used to generate a binary image from the image in the image-formable color space converted in the image conversion process, and the portrait dither pattern is included. The image processing method is characterized in that the dither patterns for landscape have a 90-degree rotation relationship with each other. 9. An image rotation conversion step of rotating a predetermined image by a predetermined angle, and an image conversion step of converting the rotated image rotated in the image rotation conversion step into an image in a color space capable of forming an image. If the predetermined image is a highlight image, a highlighting dither pattern is used to generate a binary image from the image in the image-formable color space converted in the image converting step. An image processing method characterized by: 10. The step of generating, if the predetermined image is a highlight image and is a portrait image, highlight. A binary image is generated from the image in the image-formable color space converted in the image conversion step using the portrait dither pattern, and the predetermined image is a highlight image and a landscape image. For example, the highlight. A binary image is generated from the image in the image-formable color space converted in the image conversion step using the landscape dither pattern, and the highlight. Dither patterns and highlights for portraits. The relationship between the landscape dither patterns is a 90-degree rotation relationship with each other.
The image processing method according to 1. 11. The method further comprises a detection step of detecting whether or not the predetermined image is a highlight image, wherein whether or not the predetermined image is a highlight image is determined in the generation step. The image processing method according to claim 9, wherein the determination is performed based on the detection result. 12. An image rotation conversion means for rotating and converting a predetermined image by a predetermined angle, a dither pattern rotation conversion means for rotating and converting a predetermined dither pattern by the predetermined angle, and a rotation rotated by the image rotation conversion means. An image converting means for converting an image into an image in a color space capable of forming an image, and a color space capable of forming an image converted by the image converting means using the dither pattern rotated and converted by the dither pattern rotation converting means. An image processing device for generating a binary image from the above image. 13. The image processing apparatus according to claim 12, wherein the predetermined image is an image in an RGB color space. 14. The image of the color space in which the image can be formed is
13. The image according to claim 12, which is an image in the CMY color space.
An image processing apparatus according to claim 1. 15. The image processing apparatus according to claim 12, wherein the predetermined angle is 90 degrees. 16. The image processing apparatus according to claim 12, wherein the predetermined image is a portrait image. 17. The image processing apparatus according to claim 12, wherein the predetermined image is a landscape image. 18. The image processing apparatus according to claim 12, further comprising an image forming unit that forms an image based on the image generated by the binary image generating unit. 19. An image rotation conversion means for rotating and converting a predetermined image at a predetermined angle, and an image conversion means for converting the rotation image rotated by the image rotation conversion means into an image in a color space capable of forming an image. If the predetermined image is a portrait image, a dither pattern for portrait is used to generate a binary image from the image in the image-formable color space converted by the image conversion means, and the predetermined image is If it's a landscape image,
A relationship between the portrait dither pattern and the landscape dither pattern, comprising: a generating unit that generates a binary image of the image in the image formable color space converted by the image converting unit using the landscape dither pattern Is an image processing apparatus characterized in that they are in a 90-degree rotation relationship with each other. 20. Image rotation conversion means for rotating and converting a predetermined image at a predetermined angle, and image conversion means for converting the rotated image rotated by the image rotation conversion means into an image in a color space capable of forming an image. If the predetermined image is a highlight image, it includes a generating unit that generates a binary image from the image of the image-formable color space converted by the image converting unit, using a highlight dither pattern. An image processing device characterized by: 21. When the predetermined image is a highlight image and the portrait image is a portrait image, the generating unit highlights. A binary image is generated from the image in the image formable color space converted by the image conversion means using the portrait dither pattern, and the predetermined image is a highlight image and a landscape image. For example, the highlight. A binary image is generated from the image in the image-formable color space converted by the image conversion unit using the landscape dither pattern, and the highlight. Dither patterns and highlights for portraits. The relationship between the landscape dither patterns is a 90-degree rotation relationship with each other.
0. The image processing apparatus according to 0. 22. A detection means for detecting whether the predetermined image is a highlight image is further provided, and whether the predetermined image is a highlight image is determined by the detection means by the generation means. The image processing apparatus according to claim 20, wherein the determination is made based on the detection result.